Flash memory is a type of non-volatile, electrically erasable programmable read-only memory (EEPROM), which is erased and programmed on a page or block basis.
Flash memory may include NAND type cells or NOR type cells. NAND type flash memory provides reading, unlocking, erasing, and writing to pages or blocks of memory cells. NOR type flash memory provides unlocking, erasing, and writing on pages or blocks of memory cells, and may provide reading on individual bytes or words of memory cells.
Flash memory has a finite number of erase/rewrite cycles, referred to as erase-endurance or endurance. Flash memory devices may provide wear leveling, using firmware or file system drivers to count write operations and to dynamically remap blocks of memory in order to spread the write operations among sectors.
Endurances vary between different types of memory cells. For example, flash memory may utilize either single-level cells (SLCs), which store one bit of information per cell, or multi-level cells (MLCs), which store multiple bits of information per cell. Endurance of a single level cell may be an order of magnitude greater than a two-level cell, which may be an order of magnitude greater than a three-level cell. SLC flash memory systems tend to be more expensive than MLC flash memory systems.
In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.